The present invention relates to a tremolo mechanism for a guitar by which the string tension is temporarily and gradually reduced to give a tremolo effect.
Well known conventional tremolo mechanisms for guitars are either of the so-called Fender type or the Kahler type. Of those two types, the Fender type of tremolo mechanism has, as shown in FIG. 2 and FIG. 3, an end plate 5 which consists of a bridge 2 and a string-fixing part 4 for strings 3 on the front of the body of the guitar, assembled as one unit. The end plate 5 is mounted on the guitar body 1 so that it can rotate about a fulcrum 6. The tension in the strings 3 is gradually reduced to give a tremolo effect by the rotation of the end plate 5 obtained by pressing the tremolo arm against the force of a spring 7.
With the tremolo mechanism of the Fender type shown in FIG. 3, length from the finger board to the bridge of the sixth string (3-6) is slightly longer than that of the first string (3-1) because of the placement of the bridge 2 at an angle to the parallel strings. Since the diameter of the strings 3 increases from the first string (3-1) to the sixth string (3-6), when the strings are pressed while playing the guitar, the thin first string (3-1) touches the finger board 9 even when it is pressed lightly by a finger toward the finger board 9, while the thick sixth string (3-6) must be pressed by a large force toward the finger board 9, and a round portion of the string (3-6) touches the finger board 9. The reason why the bridge 2 is positioned obliquely is to compensate for the shortening in the lengths of the string in various scales due to the rounded contact of the sixth string (3-6) with the finger board, and a thicker string requires more compensation than a thinner string. In this arrangement, the distance from the bridge 2 to the string-fixing part 4 is shorter for the sixth string (3-6) than for the first string (3-1). As a result, when the tremolo arm 8 is pressed down, the reduction in tension of the sixth string (3-6) is larger than that of the first string (3-1). However, since the first string (3-1) which has a smaller reduction in tension has a smaller diameter than the thick sixth string (3-6), and its sensitivity to tone variations due to the reduction in string tension is low, the first string has a small variation of about 2 or 3 tones. On the other hand, the sixth string which has a larger reduction in tension has a small ratio of elongation because of its larger diameter, and it is more sensitive to tone variations caused by this reduction in the tension. It may therefore give a variation of about 6 or 7 tones. For this reason, the Fender type of tremolo mechanism gives different tremolo effects for the different strings when the tremolo arm is pressed, the tremolo effects provided for the most-used strings (3-1) through (3-3) are weak but the tremolo effect for the sixth string (3-6) is too large, and sometimes the heavier strings lose too much tension and are liable to go out of tune, so that it is impossible to provide tremolo with a harmonized chord. This is a disadvantage of Fender type of mechanism.
With a tremolo mechanism of the Kahler type shown in FIG. 4, a frame 12 is fixed onto the guitar body 10 by screws 11 and a rotor 16 is mounted on the frame 12. The rotor 16 rotates about a shaft 15 when a tremolo arm 14 is pressed against the force of a spring 13. The rotor 16 is provided with a fixing part 18 that fixes each of strings 17. A bridge roller 19 that supports each string is fixed so that it does not rotate when the tremolo arm 14 is pressed down. The tremolo effect is obtained by shifting only the string-fixing part 18 by the rotation of the rotor 16, which is done by pressing the tremolo arm 14. Since the position of the bridge roller 19 is fixed in the Kahler type of mechanism, the reduction in the string tension produced by pressing the tremolo arm is the same for all the strings, and it is impossible to vary the reduction in string tension according to the differences in the rates of elongation of the strings. Consequently the Kahler type of tremolo mechanism fails to provide the same tremolo effect for all the strings, and this is a disadvantage of this type of mechanism.
Both the Fender type and the Kahler type of mechanism depend solely on spring force for returning the tremolo arm to its original position after it is released. Especially when the distance moved by the pressed tremolo arm is large, it may fail to return to its original position because the spring quality is inadequate, or for other reasons. This is another disadvantage of both types of mechanism.